Design of high-Q micromachined tunable capacitors for RF applications

Two high-Q micromachined electro-mechanically tunable capacitors are presented. The proposed designs are CMOS-compatible that can be integrated with CMOS circuit in a single die. In these structures there is no need for cantilever beams which introduce considerable series resistance to the capacitor and decrease the quality factor. So our proposed structures achieve better Q in a smaller area. The simulated 1pF full plate capacitor with aluminium deposition on top plate shows a tuning range of 42% and a Q of 47 at 1 GHz. For the comb structure the tuning range is 43% and Q is 45 at 1 GHz. Pull-in voltage is 3.5 V for both capacitors. The S
11
responses are reported for a frequency range from 1 up to 4 GHz.